This invention relates generally to improvements in a continuously variable transmission, and more specifically pertains to a variable transmission incorporating a combination of race elements and transmission roller means, which are finely adjusted and regulated through a variety of equalization means, in order to provide a more compact structure for furnishing a highly efficient output of precisely controlled torque than has heretofore been obtained.
The prior art is replete with a variety of variable speed transmission mechanisms, of the type that are rather complex in structure, but which heretofore have been mainly concerned with the arrangement and functioning of roller means between cam-like disc means for furnishing variations in the power or speed of output from the transmission, but which normally have not provided fine adjustment in the structural relationship of the various components making up the transmission, in order to enhance their efficiency of operation, and particularly for sustaining a long and useful operative life. For example, the single cavity, toroidal variable speed drive design had been derived from the dual cavity continuously variable transmission (CVT) research that had been early conducted by British Leyland and General Motors Corporation, probably over the past fifty years. Examples of these types of experimentation and research are generally disclosed in the very early patents to F. A. Hayes, such as in the U.S. Pat. No. 2,123,006, which showed and described a friction transmission mechanism, incorporating a single pair of axially spaced coaxial discs, having inward facing toroidal grooves, as used in combination with the second pair of such discs, in order to provide a variation in the output torque from its input drive mechanism. And, in order to achieve that variation in speed, and hence, the consequential torque, angular adjustment of the rollers of Hayes could be made in order to induce a variation in the speed-ratio of the mechanism. Another patent to Hayes, U.S. Pat. No. 2,123,008, shows an additional variation upon his early power transmission mechanism. In this particular patent, Hayes disclosed a mechanical mechanism for enhancing the pressure exerted upon his disc, within their toroids, in order to increase the tractive, or traction, pressures that could be produced for his corresponding load, without causing any difference in the speed-ratio positions of his shown sets of rollers.
Actually, the basic concept for the use of toroid type of drives in transmissions was early patented, back in 1877, by C. W. Hunt, as disclosed in his U.S. Pat. No. 197,472, wherein was initially shown the variable transmission of the single cavity design, that required end load forces to provide sufficient normal force on the torque rollers to transmit generated torque between the two disclosed toroids. Following this, it was Hayes, in the patents as previously disclosed, that provided some improvement upon that early concept, in an attempt to develop a commercially feasible product. But, it is well known in the industry that while both of the previously mentioned companies attempted to commercialize through practical engineering design the concept of the continuous variable transmission, particularly for use for application within automotive developments, the problem with refinements to such transmissions, so that they could operate with some degree of longevity, caused the type of problems that indefinitely postponed the installation of these type of transmissions into commercial automotive products. In other words, the components, and the fatigue of the materials used in their construction, just would not allow the standard introduction of these designs into automotive products.
Another basic reason why these prior art type of transmissions were not applicable for commercial usage at the times of their inception, was primarily due to the fact that, in addition to the other reasons as previously defined, they were just too bulky and large in their construction to provide for their effective usage in the smaller type of vehicles, such as the automobile, and truck, then available at that period of time.
Metallurgical developments in the 1950's and 1960's spawned the production of quality steels and other metals that could be used in the fabrication of the types of components that were needed to construct quality transmissions of the foregoing type, and as a result, CVT technology benefited by attaining the usage and application of the types of metals that could extend the fatigue life of the components and products assembled into transmissions of this design It was during the late 1960's that companies, such as Monsanto Company, in conjunction with select automotive companies, developed a new traction fluid/lubricant for use in conjunction with toric drives that also yet additionally enhanced the fatigue life of metals, and product component usage. It is known that General Motors planned to include such a drive for use in the transmission and control or variation of torque within more heavy vehicles, such as commercial vehicles or school busses, or the like. But, apparently funding was not available in order to see such corporate activity through to fruition. Fortunately, research companies completed the development of traction fluids such as synthetic oil to generate high friction under pressure, and can be used for this particular purpose, and such fluids, one being identified under the trademark SANTOTRAC, and available from the said Monsanto Company, is on the market today for use in traction type drives, as employed in the power transmission industry. Similar and related types of transmission fluids are available from many other companies currently.
Select automotive companies have now continued to support further research upon this type of transmission, and as a result, during the 1970's, there was developed a CVT type of transmission that incorporated a metal belt or link type drive, generally identified as the VanDoorne, as known in the trade. The VanDoorne CVT offered a compact and seemingly simple design that is easily integrated with the front wheel drive type vehicle, one which has become rather in vogue over the past decade. On the other hand, it is also known that select automotive companies, who have been pursuing this type of project for the past fifteen years, have withdrawn from the same, and taken back their reserve funding, due to the unsolved reliability problems that have prevailed and plague the operations of these type of transmissions. It is known that British Leyland has continued to conduct research in the dual cavity type of toroid design, and it is known that it plans to include it in production within bus transmissions in the very near future
Examples of the dual cavity type of toroid design are shown in Perry U.S. Pat. No. 4,272,999, and Perry has done extensive research and patenting on that type of transmission, as can be noted in his variety of U.S. patents, such as U.S. Pat. Nos. 4,297,918; 4,272,999; 4,628,766; 3,406,597; 4,570,501; 2,959,063; 3,306,119; 3,153,938; 4,499,782; 4,257,495; 3,276,279; 3,267,756; 3,203,267; and 3,184,990. As can be seen therein, most, if not all, of the designs as shown in those prior patents pertain to dual cavity type drives, using dual cavity toroid configurations for attaining variable speed power transmission. Such designs, nevertheless, do incorporate not only the drives, but also their particular control systems, in order to effect some variation in the speed, the torque ratios, and the outputs attained from the transmissions. But, as can also be particularly noted therein, much of the control means incorporated into those types of systems, as shown, are of a mechanical nature, and yet do not provide the fine regulation in the operations of a transmission of this type, which will necessarily enhance the longevity and usefulness of their application, particularly when incorporated and installed within the type of products, such as automotive products, that are run continuously and on a daily basis, and which are expected to run as such for many years, by the customers and end users.
It must be noted, that much of the work of Perry, in the dual cavity type of toroid designed transmissions, derives yet from early efforts conducted by Mr. Hayes, as previously explained. Examples of some additional earlier Hayes patents, incorporating the dual drive feature, are shown in the friction transmissions disclosed in his U.S. Pat. Nos. 1,867,149; 1,904,046; 1,856,249; 2,124,399; 2,124,398; 1,984,797; 1,698,229; 1,865,102; and 1,919,218.
The foregoing is an analysis of the early and intermediate developments made to the continuous variable transmissions, whether it be of the single toroid or dual toroid cavity types, and the extent to which they have been developed, and chronologically patented, as reflected in the identified U.S. patents.
But, the current invention, as to be hereinafter summarized, is believed and does provide rather unique refinements to the functioning of this type of transmission, and particularly incorporates a variety of equalization means that have a tendency to refine the operations and functioning of such a transmission, significantly makes it compact in design, of reduced weight, much more efficient in operation, and having significant useful and longer life, even in standard and routine commercial applications.